During the wellbore completion process, a packer is run into the wellbore to seal off an annular area. Known packers employ a mechanical or hydraulic force in order to expand a packing element outwardly from the body of the packer and into the annulus defined between the packer and the surrounding casing. In addition, a cone can be driven behind a tapered slip to force the slip into the surrounding casing to prevent packer movement. Numerous arrangements have been derived in order to accomplish these results.
A disadvantage with known packer systems is the potential for becoming unseated. In this regard, wellbore pressures existing within the annulus between an inner tubular and the outer casing act against the packer's setting mechanisms, creating the potential for at least partial unseating of the packing element.
Generally, the slip used to prevent packer movement traps an internal pressure into the packing element from the initial force used to expand the packing element. During well operations, a differential pressure applied across the packing element may fluctuate due to changes in formation pressure or operation pressures in the wellbore. When the differential pressure approaches or exceeds the initial internal pressure of the packing element, the packing element may be compressed further by the differential pressure, thereby causing it to extrude into smaller voids and gaps or exceed the compression strength of the packing element. Thereafter, when the pressure is decreased, the packing element begins to relax. However, the internal pressure of the packing element may fall below the initial level due to the volume transfer and/or the compression setting of the packing element during extrusion. The reduction in internal pressure decreases the packing element's ability to maintain a seal with the wellbore when a subsequent differential pressure is applied or when the direction of pressure is changed, i.e., uphole to downhole.
Due to these issues, packers have been designed that are able to pack-off against a hydraulic cylinder, such as a boost mechanism, which can then trap a boost force into the packer's packing element. One such packer with a boost mechanism is disclosed in U.S. Pat. No. 8,881,836, which is incorporated herein by reference.
The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.